The following two sections include what I would deem to be the most crucial elements of grammar that one must simply get right. Don't want to look like an idiot on Facebook? Well then read on and grasp these basic concepts.

You're and Your – Quite possibly the most common copy error, but also the easiest to understand when to use which one. Basically, you’re is a contraction of ‘you are’. In contrast, your means ‘belonging to you’. If you think you've used the wrong one, read your sentence. Are you talking about something which belongs to someone e.g. ‘your bag’, ‘your dog’, ‘your attitude’; or are you saying ‘you are’? Incorrect examples would include ‘your not alone’ and ‘your smart’. Still confused? Here, let Ross from Friendsexplain it to you...

They’re/Their/There – Again, using the correct version is quite simple. They’re is a contraction of ‘they are’ e.g. ‘Where are the girls?’ ‘They’re playing in the park’ (They are playing in the park). Their is similar to ‘your’, above, and is used when we are referring to something belonging to others e.g. ‘their books’, ‘their clothes’, ‘their rooms’. You could also refer this as ‘belonging to them’. There is used when we referring to a place e.g. ‘Where is Katy?’ ‘She’s over there’. It is also the opposite of ‘here’ e.g. ‘I live here, not there’. Let’s think of a sentence which has all three forms: ‘They're over there in their new house’ (They are over at that place in the new house which belongs to them). Now go back and use the wrong version of they’re, their and there and you will see that the sentence will not sound correct. A lot of people just write There for everything. If you follow these simple instructions, you won’t need to do this.

Here’s a picture which has been doing the rounds on the internet. Don’t believe everything you read on the internet though; this image may well have been doctored.

It’s and Its – This is another common one and a lot of people write ‘its’ for everything. It’s is a contraction of ‘it is’ (or less frequently, ‘it has’) e.g. ‘Where is my pen?’ ‘It’s over there on that desk’ (it is over there on that desk); ‘It’s been great talking to you’ (it has been great talking to you). Its is used just like ‘your’ and ‘their’, above, which means that it is used for talking about something belonging to an object. E.g. ‘The school has closed its doors’ (the school has closed the doors which belong to it). Why this can sometimes be confusing: if we were to say ‘the dog’s paw’, dog’s has an apostrophe to denote possession, however, if we changed this and wrote ‘its paw’, the apostrophe is gone. What we need to remember is that we use it’s for ‘it is’ and its for everything else. In the above example, ‘it’s paw’ cannot be correct as we would be saying ‘it is paw’ and this doesn't sound right. Let’s use a sentence which uses both forms: ‘It’s taking me ages to figure out its problems’ (it is taking me ages to figure out the problems belonging to it). See? It’s pretty easy to understand. :)

Here’s an example of incorrect usage, courtesy of Aeroplane Jelly:

Of and Off –While of has multiple uses, we don’t need to delve into them too much. Of can be used to denote possession or ownership e.g. ‘the Queen of England’, ‘the people of Scotland’, ‘the CEO of the company’, and ‘the pages of the book’. It can also be used to tell us what something is made up of e.g. a ‘pot of gold’, a ‘cup of tea’, and a ‘city of blinding lights’. Off is the opposite of ‘on’ and is used to refer to something being suspended - ‘turn off the lights’, or removed - ‘to wipe the sweat off your face’. Two common examples of incorrect usage of these two words are ‘take your shoes of the bed’ and ‘the bus has been running late off recently’. Notice the variation in pronunciation also. The F in of is pronounced more like a V, whereas in off, the double F is a hard F sound. Using the incorrect word can change the whole context of a sentence. Consider the meaning change in the phrases ‘Of course’ and ‘off course’.

Here's a great example of incorrect usage. I also don't think Saigon needs quotation marks, nor do I think 'Call today for an immediate inspection' needs a bullet point.

Accept and Except –The confusion here is that both words sound the same, but are almost the opposite in terms of meaning. Accept is a verb and means ‘to receive’. It can also be used to mean ‘to agree/admit’. Let’s look at two examples of each. To receive: ‘I accept your gift’ and ‘he accepted my business proposal’. To agree/admit: ‘I accept that it was my fault’ and ‘she accepted my point of view’. Except is commonly used as a preposition or conjunction, but it can also be used as a verb. As a preposition, it means ‘excluding’ or ‘apart from’ e.g. ‘I like all kinds of chocolate except dark chocolate’ and ‘he knew everyone at the party except for one person’. As a conjunction, it means ‘other than’ e.g. ‘I would come to your party except I have something else on that night’ and ‘he never calls except to borrow money’. Exceptis less commonly used as a verb but when it is, it means ‘to leave out/exclude’ e.g. ‘Keep out. Staff excepted’ and ‘you are excepted from this rule’. Can you see how these two words are practically opposites? In some situations, using the wrong word will mean your sentence has the opposite meaning of what was intended e.g. ‘this machine excepts $2 coins only’ and ‘I except your apology’.

Bought and Brought – As with a lot of things, one letter can really make a world of difference. Bought is the past tense of ‘to buy’ whereas broughtis the past tense of ‘to bring’. For example ‘I bought the cheesecake from the cake shop and I brought it home’. Common examples of incorrect usage are ‘This was bought to my attention’ and ‘We recently brought a house’. You may remember a campaign by Jeep with their constant annoying phrase “I bought a Jeep”. Well, they placed a full page ad in the Herald Sun once and it went rather awry...To conclude, if you ever get confused, ask yourself did you bring
something, or did you buy something?

Affect and Effect – This is another common word that gets mixed up and it can be tricky to know when to use each word. Simply put, affect is a verb whereas effectis a noun. Effect is usually all on its own with no endings attached to it and is usually preceded by the word ‘the’ (or
‘an’) e.g. ‘The effect of global warming’. Affect is usually used as a verb and therefore has endings associated with it e.g. affecting and affected. We'll see more examples of other words that do this later on. Let’s use a sentence which contains both forms: ‘The effect of modern technology has drastically affected the way we think’. It is uncommon to use affect all on its own, however, it is still being used as a verb when doing so e.g. ‘How will the price of shares affect the stock market?’ In this case, affect is a doing word (the price of shares is doing something to the stock market). If we wanted to use the same example to describe effect, we could say ‘The price of shares will have an effect on the stock market’. The only time I can think of where effect has an ending attached to it is in the word ‘effective’.Lastly,
remember that the phrase ‘take effect’ is not ‘take affect’. While effect
is not preceded by ‘the’ or ‘an’, what this phrase means is that something will
have an effect on something, therefore the phrase is ‘take effect’. This is the
same as ‘words to that effect’ as effect in this instance is acting as
a noun and not as a verb.

Then and Than – This is another very easy one to get right. Don’t be one of those people who use Then for everything. We use Then when referring to time or a sequence of events. One example of each: ‘We were young back then’ and ‘I brushed my teeth and then I went to school’. Than is only used when we are comparing things e.g. ‘My bag is bigger than yours’ and ‘I waited longer in the waiting room than him’. If
ever you get confused, try replacing the word then or than with ‘compared
to’. If it works, than is the word you want. If not, well then you must mean then.
‘My car is better compared to yours.’ This works so it must be ‘My car is
better than yours’. ‘I went for a swim and compared to I went to work.’ This
doesn't make much sense. We must mean ‘I went for a swim and then I went to
work’.You probably wouldn't expect Monash University to get this wrong would you?

Where, Wear, Were and We’re – With these first two, the confusion is that both words are pronounced the same. With the second two, the confusion is that they both look the same. What a difference an apostrophe can make. This being said, I have seen Whereand Werebeing confused also. Whererefers to location e.g. ‘Where are the children?’ and ‘I know where she is’. Wearis a verb and usually refers to something you put on (usually clothing). ‘I will wear my leather jacket’ and ‘Which perfume is she wearing?’ It can also refer to the condition of something becoming worse e.g. ‘My tyres are wearing out’.Were is the plural past tense of ‘are’ e.g ‘We were walking down the street’ and ‘They were minding their own business’. We’reis a contraction for ‘we are’ e.g. ‘We’re walking down the street’ (We are walking down the street) and ‘We’re going to Mark’s house’ (We are going to Mark’s house). If ever you’re confused, just think of ‘we are’ (just like above with Its and It’s). If it doesn't fit, you probably mean were. Now try and switch some of these sentences around to use the wrong word and you'll find they won’t make much sense...

Again, pronunciation is everything... Where (pronounced 'wear') does not make any sense in this instance...
The correct word is obviously 'were'.

To and Too –Another commonly confused word. Too usually means 'as well’ or ‘also' e.g. ‘me too’ but it can also mean ‘in excess of’ or basically, more than something should be e.g. ‘these shoes are too expensive’, ‘don’t think about it too much’ and ‘there are too many people talking’. To has two main uses: before a verb (in its infinitive form) e.g. ‘I want to see you dance’; ‘She likes to run’ and ‘don’t tell me what to think’ and the second use is as a preposition involving movement e.g. ‘I'm going to the park’ and ‘the cop gave the speeding fine to the driver’. Note the difference in pronunciation also. Too is kind of more elongated whereas To is very short and has more of a neutral sound. This may help in knowing when to use the right word. ‘I'm going too Spain’. No, this doesn't sound right. ‘I'm going to Spain’. ‘I want too see you in my office’. This just sounds like you're placing more emphasis on the too and thus cannot be correct. ‘I want to see you in my office’. ‘I'm to busy’. No you’re not, you’re too busy. Let’s use a sentence which uses both words: ‘It was too much effort to reach a conclusion’.One
sentence I saw at work: ‘We found that to Mark.’ This should read ‘We found
that too, Mark.’ Not only does the wrong version of too change the meaning of
the sentence, there’s also a comma missing, making the sentence not make much
sense. We will cover this scenario when we look at comma usage in the next section.
Take a look at this sign on a major company’s premises. I
have blurred out the company name. How on earth did the signwriters get this
wrong??

Lastly, take a look at the following picture, courtesy of The Body Shop. Upon first inspection, it looks like a gigantic copy error doesn't it? However, it’s actually very clever. Rather than simply saying that nature is way too beautiful, it’s saying much more than that and is basically insinuating that if you use their products (which are all natural products from the earth and non man-made), this will lead you to look beautiful, thus using nature’s way to beautiful. I think it’s very clever, anyway....

Who's and Whose –A very common mistake and I can see why as this used to confuse me all the time. Again, just like everything else, once you know the difference, you'll wonder what on earth you were confused about! Basically, the rule here is exactly the same as It’s and Its. Who’s is a contraction for ‘who is’ (or less frequently, ‘who has’) e.g. ‘Who’s at the door?’ (Who is at the door?); ‘Who’s that girl you were talking to?’ (Who is that girl you were talking to?) and ‘Who’s eaten my lunch?’ (Who has eaten my lunch?). Whose means ‘belonging to whom’ e.g. ‘Whose book is this?’ and ‘the man whose brother was a Professor’. If ever you’re still confused as to which word to use, replace the word with ‘who is’. If it works, use who’s but if it doesn't, then whose is the word you are looking for. In the above two examples, you will see that who’s will not work (Who is book is this?; the man who is brother is a Professor).

If you prefer illustrations, to the right is a great incorrect example. 'Arguing over who is lawnmower is faster'. That doesn't make sense.

Passed and Past –This is in my opinion, the trickiest one out of everything in this section. While I know when to use each one, I find it difficult to explain to people when to use each. Let’s have a go though:Passed is a verb. More specifically, the past tense of ‘to pass’ e.g. ‘I pass the shops’, ‘I passed the shops’, ‘I have passed the shops’. To use the third person: ‘Ken passed me in the hallway’ or ‘Ken passed me a piece of paper in class’. Of course, it can also refer to being successful in something as in ‘I passed my driving test’ or also it could also be used in sports e.g. ‘he passed the ball to me’. This usage is much the same as above for the piece of paper example. When you’re referring to someone who’s died, the term here is ‘passed away’, not ‘past away’.Past has many uses. It mainly refers to something that has already happened, i.e. in the past. As a noun: ‘It’s all in the past’. As an adjective: ‘This past week has seen many changes’ and ‘the opponents’ past matches’. It can also refer to a former title e.g. a past President of a club. When using past as an adverb and preposition, they act in much the same way and it means ‘beyond’ or relates to movement from point to point, or just general location. Consider the following examples: ‘Don’t go past’; ‘John ran past the house’; ‘the ball sped past the defence line’; ‘take the turning just past the school’. Past is also used when referring to time e.g. ‘Half past six’, ‘quarter past one’.

To avoid confusion with Passed and Past, I have thought of a handy tip. The moment you add a verb in front of Passed, convert it to Past. For example ‘ran past, moved past, walked past, sailed past, flew past, etc’. If you used the word ‘passed’, you would be using two verbs in a row and your sentence would look odd e.g. ‘I walked passed the car park’ and ‘the ship sailed passed the docks’. Let’s use a couple of examples to show you what I mean: ‘I passed Ken in the hallway’, but ‘I snuck past Ken in the hallway’. ‘The girl passed the group of lockers’, but ‘the girl casually strolled past the group of lockers’. In these two examples, ‘snuck’ and ‘strolled’ are acting as the verbs so ‘passed’ cannot be correct, as we have already used a verb. The only exception to this rule is when the verb is ‘have’ e.g. ‘eight years have passed since you left us’. The way I see it, have is kind of a neutral verb and doesn't really do anything, unlike the above examples I provided so this is why it’s an exception to the rule. To recap, it’s always ‘have passed’ and not ‘have past’.

I hope this makes sense and can help you know when to use each one. If you’re still stuck, please ask me and I'm happy to assist!

Here’s a funny clip from Curb Your Enthusiasm:

Should of/Could of/Would of –Last but certainly not least... All these three phrases above – and less frequently seen ‘might of’ – are all incorrect. Instead, the phrase we are looking for here is ‘Should have/Could have/Would have/Might have. E.g. 'I would have scored that goal if I could have got around the defence line’. The confusion arises because in speaking, the contracted versions of all these phrases (e.g. ‘could've’) sounds a little like ‘could of’. Do not be fooled. ‘I could of made this last night’ is incorrect. What we mean is ‘I could have made this last night’.

Let's end this section with a funny image. This one is a good example of what not to do and uses a few of my above elements.